In order to accomplish efficient communication of data between a base station and a plurality of mobile terminals, particular orthogonal codes are transmitted from the mobile stations to the base station as alert signals indicating the presence of data to be transmitted. The base station checks whether particular orthogonal codes are contained in the alert signals, and when the particular orthogonal codes are detected in the alert signals, information representing the detected orthogonal codes and the schedules for transmitting the data from the mobile terminals to the base station are transmitted from the base station to the mobile terminals as an alert response to the alert signals. When the information representing the orthogonal codes used for the alert signals are contained in the alert response transmitted from the base station to the mobile terminals, the data waiting to be transmitted is transmitted from the mobile terminals to the base station according the data transmission schedules in the alert response.
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1. A mobile terminal which communicates with a base station, the mobile terminal comprising:
an input and output unit which transmits a first signal to the base station and receives a second signal from the base station;
a processing unit, connected to the input and output unit, and which controls transmission of the first signal to the base station and reception of the second signal from the base station;
a modulator, connected to the input and output unit, and which selects a code from a plurality of codes, the selected code indicating that first data is to be sent from the mobile terminal; and
a demodulator, connected to the input and output unit,
wherein the first signal includes the code selected by the modulator, and
wherein the second signal contains second data corresponding to the selected code.
2. A mobile terminal according to
4. A mobile terminal according to
wherein the code is multiplied by a plurality of codes generated in the base station comprising a plurality of bit periods by each of the plurality of bit periods and the result of multiplication is accumulated for the plurality of bit periods in order to detect whether the selected code is included in the first signal.
5. A mobile terminal according to
6. A mobile terminal according to
7. A mobile terminal according to
8. A mobile terminal according to
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This is a continuation application of U.S. Ser. No. 10/834,001, filed Apr. 29, 2004, which is a continuation application of U.S. Ser. No. 09/512,820, filed Feb. 25, 2000, (now U.S. Pat. No. 6,813,261), which is a continuation application of U.S. Ser. No. 08/907,088, filed Aug. 6, 1997, (now U.S. Pat. No. 6,111,869).
The present invention relates to a method of mobile communication for transmitting and receiving data between a base station and a plurality of mobile terminals after having determined schedules for transmitting data, and to an apparatus therefor. Particularly, the invention relates to a method of mobile communication wherein, in transmitting a plurality of data packets from mobile terminals to the base station, the base station is informed that the data packets to be transmitted are present in the mobile terminals, and wherein the schedules for transmitting and receiving the data packets are determined and then the data packets are transmitted and received.
In the prior art, a reservation-type mobile communication system has been proposed to transmit and receive data by radio communication between a base station and a plurality of mobile terminals after having reserved data channels for transmission and reception.
The present inventors have developed a system for overcoming the problems associated with the conventional system as discussed below. The above-mentioned conventional mobile communication system of the reservation type has been provided with a plurality of channels such as a preservation channel for transmitting and receiving a reservation packet, a response channel for transmitting and receiving a response packet for the reservation packet, and data channels for transmitting and receiving data, and wherein mobile terminals which wish to transmit the data use the reservation channel to transmit the reservation packet to the base station in order to let the base station know the presence of data that are to be transmitted.
The base station that has received the reservation packet from the mobile terminal assigns a data channel and a time slot which is a transmission timing that will be used by the mobile terminal, and transmits the assigned data channel and the time slot to the mobile terminal by using the response channel.
The mobile terminal that has received a response from the base station transmits data to the base station by using the assigned data channel and the time slot. The mobile terminal of the conventional transmission system of the reservation type transmits the data by using the data channel and the time slot assigned by the base station, and avoids the collision of data on the data channel even when the data are transmitted from a plurality of mobile terminals.
In the above-mentioned conventional mobile communication system of the reservation type, however, a plurality of reservation packets collide in the base station when the reservation packets are transmitted from a plurality of mobile terminals to the base station, and the contents of the reservation packets cannot be correctly read out in the base station. Therefore, the mobile terminals must transmit reservation packets again. In order to transmit the reservation package again as described above, waiting times are set in a random fashion so that the reservation packages will not collide again. When the reservation packets collide, the transmission efficiency of data greatly decreases.
Furthermore, in the above-mentioned conventional mobile communication system of the reservation type, data for making a reservation are transmitted and received in addition to the data that are to be transmitted. Therefore, a ratio of the data that are desired to be transmitted decreases in the whole data that are transmitted and received between the base station and the mobile terminals. When the consecutive data are to be transmitted being divided into a plurality of data packages in the above-mentioned conventional mobile communication system of the reservation type, in particular, a reservation packet is transmitted for the transmission of each data packet, and the packets occupy a large ratio in the whole data transmitted and received between the base station and the mobile terminal.
A mobile communication system of the reservation type applying a code division multiple access (CDMA) has been disclosed in an article to R. Esmailzadeh, N. Doi, H. Masui, Y. Ohgoshi and T. Yano, entitled “Spread Spectrum Slot Reservation Multiple Access”, IEEE VTC, April 1996, Vol. 3, pp. 1715-1719. The outline of this system involves forming a plurality of reservation channels, response channels and data channels by using pseudo noise (PN) as a plurality of different dispersion codes, requesting the transmission of data through the plurality of reservation channels, and transmitting and receiving data by using a data channel designated by the response channel. According to the conventional mobile communication system of the reservation type using the above-mentioned CDMA, the contents of the reservation packets can be correctly read out by the base station even when a plurality of mobile terminals are transmitting reservation packets to the base station. A plurality of reservation packets received by the base station are partially overlap each other on the time axis, provided the timings deviate by more than a chip which is a minimum unit for constituting a PN signal among the reservation packets.
However, in the conventional mobile communication system of the reservation type using the above-mentioned CDMA, when the deviation of timing is not larger than a chip among the reservation packets that are partly overlapping one another, the contents of the reservation packets are not correctly read by the base station. Therefore, the mobile terminals must transmit the reservation packets again. Also, the data for making a reservation are transmitted and received in addition to the data that are to be transmitted. Therefore, the ratio of the data that are desired to be transmitted becomes low with respect to the entire amount of data transmitted and received between the base station and the mobile terminals.
The present inventors have studied the above-mentioned prior art and have found the following problems. First, in the above-mentioned conventional mobile communication system of the reservation type, it is not possible to read the contents of the reservation packets when the reservation packets simultaneously arrive at the base station from a plurality of mobile terminals. When the plurality of reservation packets collide, it becomes necessary to transmit the reservation packets again.
Second, reservation packets are transmitted for determining schedules for transmitting data. For this purpose, therefore, an output is necessary for transmitting the reservation packets in addition to an output for transmitting the data, and the communication capacity of data decreases by an amount corresponding to the electric power of transmitting the reservation packets.
An object of the present invention is to provide technology capable of efficiently transmitting and receiving data between the base station and a plurality of mobile terminals.
Another object of the present invention is to provide technology capable of detecting the individual alert signals even when a plurality of alert signals are transmitted from a plurality of mobile terminals to the base station.
Yet another object of the present invention is to provide technology capable of maintaining, at a low level, the value of the alert signals transmitted from the mobile terminals.
The following are representative examples of methods and apparatuses which realize the above-mentioned and other objects of the present invention.
(1) A method of mobile communication includes determining schedules for transmitting and receiving data, and transmitting and receiving data between a base station and a plurality of mobile terminals according to the schedules. Particular orthogonal codes are transmitted from mobile stations to the base station as alert signals indicating the presence of data to be transmitted. The base station checks whether particular orthogonal codes are contained in the alert signals transmitted from the mobile terminals to the base station. When the particular orthogonal codes are detected in the alert signals transmitted from the mobile stations to the base station, data representing the detected orthogonal codes and the schedules for transmitting the data from the mobile terminals to the base station are transmitted from the base station to the mobile terminals as an alert response in response to the alert signals. When the data representing the orthogonal codes used for the alert signals transmitted from the mobile terminals to the base station are contained in the alert response transmitted from the base station to the mobile terminals, the data transmission schedules in the alert response are read out at the mobile terminals and the data are transmitted from the mobile terminals to the base station according the schedules that are read out.
When the data are to be transmitted and received between the base station and the mobile terminals according to the above-mentioned mobile communication method, mobile terminals which intend to transmit data select and generate particular orthogonal codes out of a plurality of orthogonal codes, and transmit these generated orthogonal codes to the base station as alert signals indicating the presence of data that are to be transmitted. Here, the orthogonal codes transmitted as alert signals from the mobile terminals to the base station are such codes that the inner products of the same codes assume particular values but the inner products of different codes assume a value of zero.
The base station that has received the alert signals generates orthogonal codes and checks whether these generated orthogonal codes are contained in the alert signals transmitted from the mobile terminals to the base station. When the orthogonal codes generated by the base station are detected in the alert signals transmitted from the mobile terminals to the base station, the base station that has received the alert signals determines schedules for transmitting the data from the mobile terminals to the base station. Then the base station transmits, to the mobile terminals, the data representing the detected orthogonal codes and the determined schedules for transmitting data from the mobile terminals to the base station as an alert response to the alert signals.
Upon receiving the alert response, the mobile terminals compare the orthogonal codes transmitted from the mobile terminals to the base station with orthogonal codes represented by the data stored in the alert response, and check if the data representing the orthogonal codes used in the alert signals transmitted from the mobile terminals to the base station are contained in the alert response transmitted from the base station to the mobile terminals. When the data representing the orthogonal codes used by a mobile terminal as its alert signal are contained in the alert response from the base station, the data transmission schedules in the alert response are read out by the mobile terminal, and the data are transmitted from the mobile terminal to the base station according to the schedules that are read out.
According to the mobile communication method as described above, the data are transmitted and received after the schedules are determined by alert signals of orthogonal codes. Therefore, an efficient communication of data can be accomplished between the base station and the plurality of mobile terminals.
(2) In the mobile communication method described in (1) above, the alert signals transmitted from the mobile terminals to the base station are multiplied by each of a plurality of orthogonal codes generated in the base station in order to check whether particular orthogonal codes are contained in the alert signals. The base station generates a plurality of orthogonal codes upon receiving alert signals from the mobile terminals, multiplies the alert signals transmitted from the mobile terminals to the base station by each of a plurality of orthogonal codes generated by the base station, and detects orthogonal codes in the alert signals that are received based upon the results of multiplication.
When a plurality of mobile terminals simultaneously transmit alert signals to the base station, a plurality of orthogonal codes are contained in the alert signals received by the base station. Here, however, the inner products of the same orthogonal codes assume particular values and the inner products of different orthogonal codes assume a value of zero. Therefore, the alert signals containing a plurality of orthogonal codes are multiplied by each of a plurality of orthogonal codes generated by the base station, and the results of multiplication are checked for each of the orthogonal codes. Even when the plurality of orthogonal codes are contained in the alert signals, therefore, it is possible to check if particular orthogonal codes are contained.
According to the mobile communication method as described above, the results of multiplication of the same orthogonal codes assume particular values and the results of multiplication of different orthogonal codes assume a value of zero. This makes it possible to detect the individual alert signals even when the plurality of alert signals are transmitted from a plurality of mobile terminals to the base station.
(3) In the mobile communication method described in (2) above, the results of multiplication of the alert signals transmitted from the mobile terminals to the base station and the orthogonal codes generated in the base station, are accumulated for each of a plurality of bit periods constituting the orthogonal codes in order to check whether particular orthogonal codes are contained in the alert signals. Upon receiving alert signals from the mobile terminals, the base station multiplies the alert signals transmitted from the mobile terminals to the base station by orthogonal codes generated by the base station, and accumulates the results of the multiplication for each of a plurality of bit periods constituting the orthogonal codes. When the inner products of the orthogonal codes in the alert signals that are received and the orthogonal codes generated by the base station are accumulated for each of a plurality of bit periods, the noise component in each bit period is canceled and the S/N ratio of the alert signals is improved. Therefore, it becomes possible to maintain the output value of the alert signals transmitted from the mobile terminals at a low level. This saves the output of the alert channel for transmitting the alert signals and increases the number of data channels.
According to the mobile communication method as described above, reception of the alert signals is detected by accumulating the orthogonal codes for a plurality of bit periods, making it possible to maintain the output value of the alert signals transmitted from the mobile terminals at a low level.
(4) An apparatus used for mobile communication according to a method involving determining schedules for transmitting and receiving data, and transmitting and receiving data between a base station and a plurality of mobile terminals according to the schedules, includes an alert signal transmission means for transmitting particular orthogonal codes from mobile terminals to the base station as alert signals indicating the presence of data to be transmitted. The apparatus also includes an alert signal reception means for checking in the base station whether particular orthogonal codes are contained in the alert signals transmitted from the mobile terminals to the base station. An alert response transmission means is provided which, when the particular orthogonal codes are detected in the alert signals transmitted from the mobile terminals to the base station, transmits, from the base station to the mobile terminals, data representing the detected orthogonal codes and the schedules for transmitting the data from the mobile terminals to the base station as an alert response to the alert signals. Finally, an alert response reception means is provided which, when the data representing the orthogonal codes used for the alert signals transmitted from the mobile terminals to the base station are contained in the alert response transmitted from the base station to the mobile terminals, reads out at the mobile terminals the data transmission schedules in the alert response.
When the data are to be transmitted and received between the base station and the mobile terminals according to the above-mentioned mobile communication apparatus, mobile terminals which intend to transmit data select and generate particular orthogonal codes out of a plurality of orthogonal codes, and transmit these generated orthogonal codes to the base station as alert signals indicating the presence of data for transmitting the above generated orthogonal codes. In the base station which has received the alert signals, the alert signal reception means generates orthogonal codes and checks if the above generated orthogonal codes are contained in the alert signals that are transmitted from the mobile terminals to the base station. When the orthogonal codes generated by the base station are detected in the alert signals transmitted from the mobile terminals to the base station, the alert response transmission means in the base station that has received the alert signals determines schedules for transmitting data from the mobile terminals to the base station, and transmits, from the base station to the mobile terminals, the data representing the detected orthogonal codes and the determined schedules for transmitting data from the mobile terminals to the base station as an alert response to the alert signals.
In the mobile terminals that have received the alert response, the alert response reception means compares the orthogonal codes transmitted from the mobile terminals to the base station with orthogonal codes represented by the data stored in the alert response, and checks if the data representing the orthogonal codes used in the alert signals transmitted from the mobile terminals to the base station are contained in the alert response transmitted from the base station to the mobile terminals. When the data representing the orthogonal codes used by the mobile terminals as alert signals are contained in the alert response from the base station, the data transmission schedules in the alert response are read out by the mobile terminals, and the data are transmitted from the mobile terminals to the base station according to the schedules that are read out.
According to the mobile communication apparatus as described above, the data are transmitted and received after the schedules are determined by alert signals which use orthogonal codes. Therefore, an efficient communication of data can be accomplished between the base station and the mobile terminals.
(5) In an apparatus for mobile communication described in (4) above, the alert signal reception means is provided with a multiplication means for multiplying the alert signals transmitted from the mobile terminals to the base station by each of a plurality of orthogonal codes generated in the base station. When the base station in the above-mentioned mobile communication apparatus receives alert signals from the mobile terminals, the alert signal reception means generates a plurality of orthogonal codes, and the multiplication means multiplies the alert signals transmitted from the mobile terminals to the base station by each of a plurality of orthogonal codes generated by the base station, in order to detect orthogonal codes in the alert signals that are received based upon the results of multiplication. When a plurality of mobile terminals simultaneously transmit alert signals to the base station, a plurality of orthogonal codes are contained in the alert signals received by the base station. Here, however, the inner products of the same orthogonal codes assumes particular values and the inner products of different orthogonal codes assume a value of zero. Therefore, the alert signals containing a plurality of orthogonal codes are multiplied by each of a plurality of orthogonal codes generated by the base station, and the results of multiplication are checked for each of the orthogonal codes. Even when the plurality of orthogonal codes are contained in the alert signals, therefore, it is possible to check if particular orthogonal codes are contained.
According to the mobile communication apparatus as described above, the results of multiplication of the same orthogonal codes assume particular values and the results of multiplication of different orthogonal codes assume a value of zero. This makes it possible to detect the individual alert signals even when the alert signals are transmitted from the mobile terminals to the base station.
(6) In the mobile communication apparatus described in (5) above, the alert signal reception means is provided with an accumulation means for accumulating the results of multiplication of the alert signals transmitted from the mobile terminals to the base station and the orthogonal codes generated in the base station for each of a plurality of bit periods constituting the orthogonal codes. When the base station receives alert signals from the mobile terminals, the alert signal reception means multiplies the alert signals transmitted from the mobile terminals to the base station by orthogonal codes generated by the base station, and the accumulation means accumulates the results of multiplication for each of a plurality of bit periods constituting the orthogonal codes. When the inner products of the orthogonal codes in the alert signals that are received and the orthogonal codes generated by the base station are accumulated for each of a plurality of bit periods constituting the orthogonal codes, the noise component in each bit period is canceled and the S/N ratio of the alert signals is improved. Therefore, it becomes possible to maintain the output value of the alert signals transmitted from the mobile terminals in the mobile communication apparatus at a low level. This saves the output of the alert channel for transmitting the alert signals and increases the number of data channels.
According to the mobile communication apparatus as described above, reception of the alert signals is detected by accumulating the orthogonal codes for a plurality of bit periods, making it possible to maintain the output value of the alert signals transmitted from the mobile terminals at a low level.
These and other objects, features and advantages of the present invention will become more apparent in view of the following detailed description of the preferred embodiments in conjunction with the accompanying drawings.
The following detailed description of the preferred embodiments is undertaken in connection with the drawings.
A mobile communication method and an apparatus therefor according to an embodiment of the present invention will now be described in which alert signals representing requests of transmission are transmitted from a plurality of mobile terminals to a base station to determine transmission schedules. Then, data packets are transmitted and received by radio communication between the base station and the plurality of mobile terminals.
Mobile terminals 110 to 112, which intend to transmit data packets, transmit orthogonal codes as requests for transmission 120-122 to the base station 100 to let the base station 100 know that data packets that are to be transmitted are present in the mobile terminals 110 to 112. The base station 100 that has received the requests for transmission 120-122 from the mobile terminals 110 to 112 forms transmission schedules 130 to 132 by determining time slots and data channels used by the mobile terminals 110 to 112, and sends these formed transmission schedules 130 to 132 to the mobile terminals 110 to 112. The mobile terminals 110 to 112 that have received transmission schedules 130 to 132 from the base station 100 transmit data packets according to the time slots and data channels indicated by the transmission schedules 130 to 132 that are received.
CPU 201 controls the operation of the base station 100. Memory 202 stores a control program for controlling the operation of the base station 100. Display unit 203 displays the operating condition of the base station 100. Input/output unit 204 processes the input and output of operation instructions to and from the base station 100. DSP 205 controls the communications to mobile terminals 110 to 112. The mobile communication switching station interface unit 206 provides connection to the mobile communication switching station. All of these elements are interconnected as shown in the
Base station 100 communicates to mobile terminals 110 to 112 using code division multiple access (CDMA). Provided between the base station 100 and mobile terminals 110 to 112 are a pilot channel, an ACK/NACK or alert response channel, an alert channel and a plurality of data channels. Connected to the DSP 205 of the base station 100 are the following: the pilot channel modulator 211, ACK/NACK or alert response channel modulator 212, data channel modulator 213, alert channel accumulator 214, PN code generator 215, and data channel-matched filters 241 to 243. The pilot channel modulator 211 modulates the pilot channels for transmitting pilot signals that are received by the mobile terminals 110 to 112. The ACK/NACK or alert response channel modulator 212 modulates ACK/NACK or alert response channel for transmitting ACK/NACK which indicates success/failure of the reception of data packets from the mobile terminals 110 to 112 as well as alert response to the alert signals received from the mobile terminals 110 to 112. The ACK/NACK or alert response channel modulator 212 corresponds to the alert response transmission means which, when particular orthogonal codes are detected in the alert signals transmitted from the mobile terminals 110 to 112 to the base station 100, transmits, from the base station 100 to the mobile terminals 110 to 112, the data representing the above detected orthogonal codes and schedules for transmitting data packets from the mobile terminals 110 to 112 to the base station 100 as an alert response.
The data channel modulator 213 modulates a plurality of data channels for transmitting data packets received from the mobile terminals 110 to 112. The alert channel accumulator 214 accumulates signals of alert channels received through the alert channel-matched filter 250, and corresponds to the alert signal reception means which checks whether particular orthogonal codes are contained in the alert signals transmitted from the mobile terminals 110-112 to the base station 100. The PN code generator 215 generates a PN code which differs depending upon the pilot channel, alert channel, ACK/NACK or alert response channel and data channels. The data channel-matched filters 241 to 243 take out transmission data in agreement with the PN codes of a plurality of data channels.
A pilot signal modulated by the pilot channel modulator 211 and a PN code for pilot channel generated by the PN code generator 215 are multiplied by the multiplier 221, passed through the adder 231 and the multiplier 224, and are transmitted as pilot signals to the mobile terminals 110 to 112 from an antenna 210 at a down carrier frequency ff. Similarly, the ACK/NACK or alert response modulated by the ACK/NACK or alert response channel modulator 212, data packets modulated by the data channel modulator 213, and a PN code for ACK/NACK or alert response channel and a PN code for a data channel generated by the PN code generator 215, are multiplied through the multipliers 222 and 223, passed through the adders 231, 232 and the multiplier 224, and are transmitted to the mobile terminals 110 to 112 from the antenna 210 at a down carrier frequency ff.
The signals transmitted from the mobile terminals 110 to 112 at an up carrier frequency fr and received by the antenna 210, are separated into signals of the data channels and signals of the alert channel by PN codes for data channels and a PN code for the alert channel generated by the PN code generator 215, the data channel-matched filters 241-243 and the alert channel-matched filter 250. Then, the signals of the data channels are input into the DSP 205 and the signals of the alert channel are input into the alert channel accumulator 214.
The pilot channel demodulator 413 demodulates the pilot signals transmitted from the base station 100 over pilot channels. The data channel demodulator 414 demodulates the data packets transmitted from the base station 100 over the data channels. The ACK/NACK or alert response channel demodulator 415 demodulates the ACK/NACK or alert response transmitted from the base station 100 over the ACK/NACK or alert response channel, and corresponds to the alert response reception means which reads the data packet schedules in the alert responses in the mobile terminals 110 to 112 when the data representing orthogonal codes used for the alert signals transmitted from the mobile terminals 110-112 to the base station 100 are contained in the alert responses transmitted from the base station to the mobile terminals 110-112. The PN code generator 416 generates a PN code which differs depending upon the pilot channel, alert channel, ACK/NACK or alert response channel and data channels.
In the mobile terminals 110 to 112, a data packet signal modulated by the data packet transmission modulator 411 is multiplied by a PN code for data channel generated by the PN code generator 416 through the multiplier 421, passed through the adder 431 and the multiplier 423, and is transmitted to the base station 100 from an antenna 410 at an up carrier frequency fr. Similarly, an alert signal modulated by the alert channel modulator 412 is multiplied by a PN code for the alert channel generated by the PN code generator 416 through the multiplier 422, passed through the adder 431 and the multiplier 423, and is transmitted to the base station 100 from the antenna 410 at the up carrier frequency fr.
As the mobile terminals 110 to 112 receive, through antenna 410, a signal transmitted from the base station 100 at the down carrier frequency ff, the multiplier 425 multiplies this received signal by the PN code for the pilot channel generated by the PN code generator 416, the pilot channel demodulator 413 demodulates the pilot signal, and the slot synchronizing data is input to the DSP 405. Similarly, a multiplier 426 multiplies a signal transmitted from the base station 100 at the down carrier frequency ff by a PN code for the data channel generated by the PN code generator 416, and the data packet signal is demodulated by the data channel demodulator 414 and is input to the DSP 405. Furthermore, a signal transmitted from the base station 100 at the down carrier frequency ff is multiplied by a PN code for the ACK/NACK or alert response channel generated by the PN code generator 416 through the multiplier 427, and the ACK/NACK or alert response is demodulated by the ACK/NACK or alert response channel demodulator 415 and is input to the DSP 405.
In the alert channel accumulator 214 of the base station 100 of
On the other hand, when the inner products of the alert channel signals input through the alert channel-matched filter 250 and the orthogonal codes 601 to 604 are accumulated for each of a plurality of bit periods 611, the noise component is canceled in each bit period 611, and the S/N ratio of the alert channels is improved. When the codes of, for example, 32 bits are used as orthogonal codes 601 to 604, the accumulation is effected for each of 32 bit periods 611 and a gain of about 15 dB is obtained. It is therefore allowed to decrease the output of the alert channel for transmitting alert signals of the side of mobile terminals 110 to 112 and, hence, to increase the number of data channels for transmitting and receiving data packets.
Described below is a schedule response operation for transmitting alert signals from the mobile terminals 110-112 to the base station 100 and for transmitting the data packets from the base station 100 to the mobile terminals 110-112 in the mobile communication apparatus of the present invention
Next, the accumulators 321 to 324 in the alert channel accumulator 214 accumulate the results of accumulation for each bit period 611 and output the results of accumulation. The results of accumulation of the accumulators 321 to 324 assume particular values when the received alert signals contain an alert signal formed by the orthogonal codes which are the same as the orthogonal codes 601 to 604 generated by the orthogonal code generator 300. Therefore, when the orthogonal codes 601 to 603 are transmitted as alert signals from the mobile terminals 110 to 112 as described above, the accumulators 321 to 323 output particular values as results of accumulation, and the output of the accumulator 324 becomes zero.
Here, the time slot 903 “t+3”, of
Then, at step 1103, it is checked whether the alert response from the base station 100 is received by the ACK/NACK or alert response channel demodulator 415. When there is no response from the base station 100, the procedure proceeds to a processing at a step 1104. In the processing at step 1104, the DSP 405 in the mobile terminals 110 to 112 temporarily discontinues the processing until a time corresponding to N slots (N is a random number) passes. The procedure then returns back to step 1102 where the orthogonal codes 601 to 603 are transmitted to the base station 100 as alert signals from the head of the slot timings represented by the pilot signals. At step 1103, the ACK/NACK or alert response channel demodulator 415 checks if the alert response from the base station 100 is received or not. When the response from the base station 100 is received, the procedure proceeds to step 1105.
At step 1105, the DSP 405 in the mobile terminals 110 to 112 reads an orthogonal code number 902 in the alert response from the base station 100, and checks if the orthogonal code number 902 that is read out represents the alert signal of a mobile terminal. When the orthogonal code number 902 in the alert response from the base station 100 represents the alert signal of the mobile terminal, data packets are transmitted from the data packet transmission modulator 411 to the base station 100 by using the time slots 903 and the data channel number 904 in the alert response.
At step 1106, the DSP 405 of the mobile terminals 110 to 112 checks if the base station 100 has successfully received the data packets that are transmitted or not. When the NACK from the base station 100 has been received by the ACK/NACK or alert response channel demodulator 415, the procedure returns back to the processing at the step 1105 and the data packets are transmitted again. When the ACK from the base station 100 has been received by the ACK/NACK or alert response channel demodulator 415 as a result of checking if the base station 100 has successfully received the data packets that are transmitted in the processing at the step 1106, the processing for transmitting the data packets ends.
Then, at step 1203, an address 901 of the transmitting source representing the address of the base station 100, orthogonal code numbers 902 representing the orthogonal codes 601 to 603 that are received, and the above determined time slots 903 and data channel numbers 904, are sent as schedules to the mobile terminals 110 to 112 through the ACK/NACK or alert response channel modulator 212. At step 1204, the DSP 205 in the base station 100 checks if the data packets from the mobile terminals 110 to 112 are received through the data channel-matched filters 241 to 243 or not. When the data packets have not been received by the above determined time slots 903 and data channel numbers 904, the procedure proceeds to step 1205. At step 1205, the DSP 205 in the base station sends, through the ACK/NACK or alert response channel modulator 212, the NACK to the mobile terminals from which no data pack was received and effects the re-scheduling. Then, the results of the re-scheduling are sent to the mobile terminals, and the procedure is returned back to step 1204.
The process proceeds to step 1206 when the data packets are received through the data channel-matched filters 241 to 243 as a result of checking, at step 1204, whether the data packets are received from the mobile terminals 110 to 112. At step 1206, the DSP 205 in the base station 100 checks if the data packets are successfully received or not. When an error is occurring during the transmission of the data packets, the process proceeds to step 1207. At step 1207, the DSP 205 in the base station 100 transmits, through the ACK/NACK or alert response channel modulator 212, the NACK to the mobile terminals that have transmitted erroneous data packets, and effects the re-scheduling. After the results of the re-scheduling are sent to the mobile terminals, the procedure is returned back to step 1204. When no error occurs during the transmission of the data packets as a result of checking, at step 1206, whether the data packets are successfully received or not, the process proceeds to step 1208 where the ACK is transmitted to the mobile terminals 110 to 112, and the processing for receiving the data packets ends.
According to the mobile communication apparatus of the present invention as described above, the data are transmitted and received after having determined the schedules by alert signals of orthogonal codes. Therefore, efficient communication of data is accomplished between the base station and a plurality of mobile terminals. Additionally, the results of multiplication of the same orthogonal codes assume particular values and the results of multiplication of different orthogonal codes assume a value of zero. Even when a plurality of alert signals are transmitted from a plurality of mobile terminals to the base station, it is possible to detect the individual alert signals. Furthermore, the reception of the alert signals is detected by accumulating the orthogonal codes of a plurality of bit periods making it possible to maintain, at a low level, the values of the alert signals transmitted from the mobile terminals.
The effects obtained by the disclosed embodiment of the present invention are briefly set forth as follows.
(1) The data are transmitted and received after having determined the schedules by alert signals of orthogonal codes. Therefore, efficient communication of data is accomplished between the base station and the plurality of mobile terminals.
(2) The results of multiplication of the same orthogonal codes assume particular values and the results of multiplication of different orthogonal codes assume a value of zero. Even when a plurality of alert signals are transmitted from a plurality of mobile terminals to the base station, therefore, it is possible to detect the individual alert signals.
(3) The reception of the alert signals is detected by accumulating the orthogonal codes of a plurality of bit periods making it possible to maintain, at a low level, the values of the alert signals transmitted from the mobile terminals.
While the present invention has been described above in conjunction with the preferred embodiment, one of ordinary skill in the art would be enabled by this disclosure to make various modifications to this embodiment and still be within the scope and spirit of the invention as defined in the appended claims.
Yano, Takashi, Doi, Nobukazu, Esmailzadeh, Riaz
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